Generally, in an industrial robot (hereinafter, refer to as “robot” in an abbreviating manner), there is wired various filament bodies such as an electric cable used in a motor driving each of joint axes of a robot and a welding feeding apparatus and various sensor devices mounted on the robot, a fluid conduit pipe for supplying an air, a gas or the like, and the like.
Further, these wiring filament bodies have such a constraint condition as a radius of bending and a rotational motion range taking a mechanical durability into consideration, caused by being exposed to a bending motion and a twisting motion at a time when the joint portion of the robot executes a rotational motion, and it is necessary to take into consideration the dustproof and waterproof structure of the joint portion of the robot, in correspondence to an environment in which the industrial robot is arranged and an intended use of the industrial robot.
In this case, as a conventional dustproof and waterproof structure of the joint portion of the robot, there has been known a method of wiring a filament body through a through hole provided in a center portion of a joint, and closing an arm opening portion by a cover and a packing (for example, refer to patent document 1).
However, in the conventional structure mentioned above, since the through hole for passing the filament body therethrough is provided coaxially with a joint axis, it is necessary to arrange a drive motor so as to keep clear of a center portion of the joint axis. Accordingly, power transmitting parts such as a pulley, a timing belt and the like and a bearing mechanism are increased, and it is unavoidable that a cost of the robot becomes wholly high.
Further, since the structure of the joint portion is complicated, the joint portion is enlarged in size and a mass thereof is increased. Further, since the filament body is passed through the through hole provided in a speed reducing gear, there is generated a necessity of employing a large-size speed reducing gear having a large through hole, in the case where the number of the filament bodies is increased and the filament bodies cannot pass through the through hole. Accordingly, there is generated a necessity of employing large-sized members in the other members such as the pulley, the motor and the like. As a result, the joint portion is enlarged in size and the mass of the joint portion is increased. Since its own weight of the robot having a high weight generates its own load, a motion performance of the robot is lowered.
Patent Document 1: Unexamined Japanese Patent Publication No. 11-254377